3. General precautions to be taken during sampling operations

All operations related to sampling should be performed with care, using proper equipment and tools. Any contamination of the sample by dust or other foreign material is liable to jeopardize the validity of the subsequent analyses.

For the sampling of products at warehouses, the responsible person should have at his or her disposal all the tools needed to open the packages, barrels, containers, etc., including knives, pliers, saws, hammers, wrenches, implements to remove dust (such as brushes), and material to reclose the packages (such as sealing tape), as well as self-adhesive labels to indicate that a part of the contents has been removed from a package or container.

Sampling of uniform starting materials does not require complicated tools. A variety of pipettes fitted with suction bulbs, cups or beakers, dippers, and funnels are needed for liquids of low viscosity. A glass rod can be used for highly viscous liquids; and spatulas or scoops are needed for powdered and granular solids. A porcelain or stainless steel spoon which can be sterilized by heating is suitable for sampling sterile powders.

Tools for sampling nonuniform materials are more complicated and more difficult to clean. A sampling tube with a shutter at the lower end is used to sample liquids in drums or other large containers. The tube is inserted vertically to the full depth of the drum, the lower end is then closed and the core removed. To sample solids, a slotted tube with a pointed end is used. It is inserted horizontally with the slot downmost and then turned through 180°. When withdrawn, it captures material along its entire length. A double-tubed trier may also be used to remove a portion from the whole length of a large container. Before being sampled, lumped solids must be ground to powder in a mortar.

All tools and implements should be kept scrupulously clean. Before re-use they should be thoroughly washed, rinsed with water or a suitable solvent, and dried. Adequate washing facilities should be provided in warehouses, otherwise inspectors will need to bring separate clean sets of sampling implements for each product.

Sampling from large containers of starting material or bulk products can present difficulties. Whenever possible, this work should be carried out in a separate closed cubicle within the warehouse in order to reduce the risk of contamination by dust of either the sample or the remaining material in the container, or cross-contaminations. For sterile materials, sampling should be carried out under aseptic conditions.

Sampling of drug products in retail containers from outlets such as pharmacies or hospitals in general does not present problems, save that the inspector should ensure that the material taken is sufficient for the intended analyses and for the retention samples, and that all sampling units are derived from the same batch.